Power Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) include drift regions, which are lightly doped with a p-type or an n-type impurity. The concentrations of the drift regions are low, so that the breakdown voltages of the power MOSFETs are increased. A conventional MOSFET has a Shallow Trench Isolation (STI) region extending below the respective gate electrode. A drain-side drift region extends underlying the gate electrode, and adjoins a channel region that has an opposite conductivity type than the drain-side drift region. The channel region also extends underlying the gate electrode.